An atomic scale understanding of the surface degradation mechanism during cathodic corrosion of a platinum electrode is still lacking. Here, we present results of surface structural changes observed during cathodic polarization of a polycrystalline Pt electrode and single crystalline Pt(111) in acid electrolytes in the absence and presence of cations (Na⁺) by in situ electrochemical atomic force microscopy (EC-AFM) imaging. The electrolyte cation is proved to be a prerequisite to trigger cathodic etching of the polycrystalline Pt surface. Further examination of the evolution of electrochemical signals and distinct surface structural transformations of an atomically defined Pt(111) single-crystal electrode during cathodic corrosion reveals clearly that the roughening process commences at the under-coordinated sites of the Pt(111) surface. The created triangular-shape pattern, actually a 100-oriented pit in a 111-terrace, grows primarily laterally in the initial regime, while prolonged cathodic corrosion leads to the existing etching pits growing in depth until ultimately they coalesce with each other, generating a highly roughened surface.

中文翻译：

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Pt(111) 和多晶 Pt 在酸溶液中阴极腐蚀初始阶段的原位 EC-AFM 研究

仍然缺乏对铂电极阴极腐蚀过程中表面降解机制的原子尺度理解。^{在这里，我们展示了在不存在和存在阳离子 (Na +} ) 的情况下原位在酸性电解质中多晶 Pt 电极和单晶 Pt(111) 的阴极极化过程中观察到的表面结构变化的结果电化学原子力显微镜 (EC-AFM) 成像。电解质阳离子被证明是触发多晶 Pt 表面阴极蚀刻的先决条件。进一步检查电化学信号的演变和原子定义的 Pt(111) 单晶电极在阴极腐蚀期间的明显表面结构转变清楚地表明粗糙化过程开始于 Pt(111) 表面的欠协调位点。创建的三角形图案，实际上是 111 梯田中的 100 定向凹坑，在初始状态下主要横向生长，而长时间的阴极腐蚀导致现有蚀刻凹坑向深处生长，直到最终它们相互结合，产生高度粗糙的表面。